Ethernet is an emerging opportunity for telecommunication carriers. This service provides point-to-point and point-to-multipoint Ethernet connectivity and offers different types of services with many combinations of quality objectives, such as loss, delay and bandwidth. This opportunity is created by the access network quickly becoming a bottleneck as new applications demand more and more bandwidth. Traditional access equipment using SDH and xDSL do not offer the speeds required to transport all the new multimedia applications such as triple-play, Fixed-Mobile-Convergence (FMC) and IP multimedia sub-systems (IMS).
To address these access challenges, telecommunications carriers have selected Ethernet as the technology to rapidly deploy a wide-ranging variety of services and applications without the need to constantly modify the network infrastructure. Enterprises have long used Ethernet as the technology to support a variety of applications requiring different qualities of service (QoS) from the network. Carriers are leveraging this flexibility and are standardizing on this technology to offer data access services.
Using this service definition, existing network elements which offer network access using Ethernet technology are not designed to make maximum use of the legacy network links existing at the edge of the carrier networks. Many access technologies such as DSL or WiMAX are prone to errors which affect the link speed. The network devices are unable to react to these errors to ensure that the service level agreements are met. The following inventions are focused on addressing these challenges.
When a telecommunications provider offers an Ethernet LAN (E-LAN), a service level agreement (SLA) is entered with the customer, defining the parameters of the network connections. As part of this agreement, a bandwidth profile is defined in terms of Committed Information Rate (CIR), Committed Burst Size (CBS), Excess Information Rate (EIR) and Excess Burst Size (EBS). The CIR guarantees a minimum bandwidth to a connection while the EIR allows the connection to send at higher bandwidth when available.
Current Ethernet network implementations handle congestion locally where it occurs, by discarding overflow packets. Also, E-LAN requires duplication to support unicast miss, multicast and broadcast. This wastes bandwidth in the network in two ways:
1. bandwidth capacity is wasted as a result of retransmission of packets by higher layer protocols (e.g., TCP), and
2. packets are lost throughout the network, wasting precious upstream bandwidth which could be used by other connections generating more revenues for the carriers.
In order to meet the QoS, the Service Provider (SP) allocates an amount of bandwidth, referred to herein as the Allocated Bandwidth (ABW), which is a function of the CIR, CBS, EIR, EBS and the user line rate. Unless CBS is extremely small, the ABW is greater than the CIR in order to guarantee the QoS even when connections are bursting within the CBS.
To implement the Ethernet service in a provider's network, sufficient bandwidth needs to be allocated to each connection to meet the QoS, even though not always used, leading to inefficiencies. The service provider generally over-provisions the network in order to ensure that sufficient traffic gets through such that the application performance does not deteriorate.
When a customer subscribes to an E-LAN to receive connectivity between multiple sites, the SP needs to allocate an amount of bandwidth at least equal to ABW for each possible path in the E-LAN in order to mesh all the sites, making the service unscalable and non-profitable. E-LAN can also provide different bandwidth profiles to different sites where a site needs to send more or less information. One site can talk at any time to another site (point-to-point or “pt-pt”—by using unicast address of the destination), or one site can talk at any time to many other sites (point-to-multipoint or “pt-mpt”—by using Ethernet multicast address). Also one site can send to all other sites (broadcast—by using Ethernet broadcast address).
In FIG. 1, an E-LAN is provisioned among five customer sites 101 (sites 1, 2, 3, 4 and 5) in a network consisting of five nodes 102 (nodes A, B, C, D, E and F) connected to each other using physical links 103. The E-LAN can be implemented using VPLS technology (pseudowires with MPLS or L2TP) or traditional crossconnects with WAN links using PPP over DSC. The E-LAN can also be implemented using GRE, PPP or L2TP tunnels.
For this example, the physical links are 100 Mbps. The customer subscribes to an E-LAN to mesh its sites with a CIR of 20 Mbps and an EIR of 50 Mbps. In order to guarantee that each site can transmit the committed 20 Mbps and the burst, the SP needs to allocate a corresponding ABW of 30 Mbps between each possible pair of sites 104 such that if site 1 sends a burst to site 5 while site 4 sends a burst to site 5, they each receive the QoS for the 20 Mbps of traffic. Since any site can talk to any other site, there needs to be sufficient bandwidth allocated to account for all combinations. Therefore, in this example, (n−1)×ABW needs to be allocated on the links 104 between B and C, where n is the number of sites in the E-LAN. This situation is clearly un-scalable, as shown in FIG. 1 where the 100 Mbps physical links can only support a single E-LAN.